how to move origin point to center of object
I think your problem is this one:

Your armature has an origin, like any object. If you move and animate the whole armature in Object mode the origin will follow, because its position is linked to the object. But if you go within the object in Pose mode and begin to move the bones, it won't affect the origin position in any way, because the origin is linked to the armature position, not to the bones position within the armature, so with some animations the bones can move far away from the origin.

Generally, when you animate in Pose mode, you don't move the root bone, so this bone will stay close to the origin. But if you begin to move it, for a reason or another, it may also move far away from the origin.

If you want to see what is the real position of the bones within your armature, relatively to the origin, go in Pose mode, select all your bones and press altR, altG and altS, or in the Properties panel > Data > Skeleton, press Rest Position, or switch to Edit mode... you'll come back to the rest position and you'll see that the bones will probably come back close to the origin, so you'll probably won't find any reason to move the origin position.

Now if, in rest position, the origin position doesn't please you, which in my opinion is probably not your problem here, you can change it: Switch to Edit mode, then, like for any other object you need to put the 3D cursor where you want the origin to be, then shiftctrlaltC> Origin to 3D Cursor.